Patent Document 1 discloses a method for producing a substituted benzoic acid from 2,4-substituted hydroxybenzoic acid ester as a starting material. This production method has problems such that methyl dichlorobenzoate as a starting material is hardly prepared and is industrially hardly available, anhydrous sodium thiomethoxide used for alkylthiolation of the starting material is industrially hardly available, and the selectivity of the alkylthiolation is low and the yield is low.